Per-account configuration lets you instruct the SSH server to treat your account differently. Using public-key authentication, you can permit or restrict connections based on a client's key, hostname, or IP address. With forced commands, you can limit the set of programs that a client may run in your account. You can also disable unwanted features of SSH, such as port forwarding, agent forwarding, and tty allocation.
Using hostbased authentication, you can permit or restrict particular hosts or remote users from accessing your account. This uses the file ~/.shosts or (less optimally) ~/.rhosts. However, the mechanism is less secure and less flexible than public-key authentication.